Two sumo wrestlers hold the top score in a new review of how much muscle the human body can carry. Their fat-free mass index, a measure of lean tissue scaled to height, came in above 36. A drug-tested college football player reached 31.7.

Researchers led by Eric Trexler published those figures in the Strength and Conditioning Journal this year. Men's fitness media has spent the week arguing about the male ceiling. Viva read the paper for a different reason. The numbers show how far a woman would have to travel to look "bulky." The distance is enormous. The real risk in your thirties runs the other way: building too little, too late.

How much muscle can you gain naturally?

For thirty years the gym answer was 25. The number came from a 1995 study of 74 male lifters who had never used steroids, and none of them scored above it.

The same paper estimated the scores of 20 Mr. America winners from 1939 to 1959, before steroids reached bodybuilding. They averaged 25.4, which spoiled the ceiling before anyone had finished building it. The new paper puts the practical limit for drug-free men nearer 28.5. Drug tests can be dodged, so even that figure carries an asterisk.

Your number is probably about 15

Most women never learn their score, so the female data is the part worth your attention.

Who Fat-free mass index
Women aged 18 to 34, general population 15.4
Female college athletes, average 18.8
Top 2.5 per cent of female college athletes 23.9
Drug-free men, practical ceiling about 28.5

Take a woman who is 165 cm tall. For her, one point on the scale equals roughly 2.7 kilos of lean tissue. Climbing from a typical score to the top of the athlete range means adding about 23 kilos of it.

Drug-free men in the paper gain about 1.4 kilos in their first 12 weeks of lifting. Women build at the same pace relative to their size, according to a 2020 analysis of studies comparing the sexes. On a smaller frame, that means fewer kilos. Gains also slow after the first year. "Bulky" sits years of near-perfect effort away, and nobody arrives there by accident on a Tuesday.

Doing nothing has a cost of its own. Lean tissue slips with age, a process doctors call sarcopenia, and sitting still speeds it up. Canada's 24-Hour Movement Guidelines ask adults for strength work at least twice a week.

Thursday, 6:40 p.m., the dumbbell rack

You reach for the 5 kg pair out of habit. The review suggests a weight you can lift six to 12 times, where the final rep is a genuine struggle. When twelve feels easy, the weight goes up.

Food does half the job. RAW Organic Protein in Vanilla blends with a banana and cold milk into something closer to a milkshake. Taste is the only reason anyone is still drinking protein in week six.

Creatine is one of two supplements Trexler's team rates as proven for growth. Protein is the other. NOW Creatine Monohydrate Pure Powder is a single unflavoured ingredient that vanishes into morning coffee. Expect the scale to creep up in the first weeks, because creatine draws water into the working tissue.

Pick up the 8 kg pair. Your score will barely notice this year, and the woman climbing stairs at 70 will thank you.

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Frequently asked questions

How do I work out my fat-free mass index?

Divide your lean mass in kilograms by your height in metres, squared. Lean mass is your body weight minus your fat mass. A DEXA body-composition scan gives the most reliable reading. Bathroom scales that estimate body fat are far less precise, so treat their number as a rough guide.

Can a woman naturally score higher than 24?

Yes. In a 2019 study of 372 female college athletes, the highest score was 27.2. The 23.9 cut-off simply marks the point that only about one athlete in 40 passes. Higher body fat also lifts the score, so compare yourself at a similar leanness.

How much protein does building muscle take?

The 2026 review recommends 1.6 to 2.2 grams of protein per kilogram of body weight each day. For a 65 kg woman, that works out to roughly 105 to 145 grams, spread across meals, with enough carbohydrate to fuel training.

This article is for information only and does not replace advice from your doctor or a registered dietitian.

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